Welder



April 23, 940- E. A. HOBART 2,197,888

WELDER Original Filed NOV. 17, 1936 3 Sheets-Sheet 1' L: La

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April 1940- E. A. HOBART I 2.197.888]

WELDER Original Filed No v 17, 1936 s Sheets-Sheet ,3

ACROSS TH! LINE STARTING JMM EDWARDAHOBAR nwu 91/ 1 1 sup-bum STARTING Patented Apr. 23, 1940 PATENT OFFICE warm new a. Hobart, m, on, mum to 11 Hobart Bras. Company, Troy, Ohio, a corpora- Original application November 11, ms, Serial 111,285. Divided and this application March 24, 1937. Serial No. 132.799

'10 Claims.

This invention relates to welding apparatus, and in particular, to welders having a plurality of circuit arrangements for adapting the welder to diifering load requirementa.

One object of this invention is toprovide an arc welder having a plurality of arrangements for the driving motor circuit, these arrangements being controlled by a switch which is actuated automatically in response to the variation in load requirement of the welder.

Another object is to provide an arc welder having a driving motor in circuit with a stardelta switch which is automatically shifted in response to the attainment of a predetermined load from star connection to delta connection, this shifting being accomplished, in one embodiment of the invention, by an electro-magnetic shiiting arrangement arranged to give a time delay between the starting of the motor and the shifting from the star to the delta connecting arrangement.

Another object is to provide an arc welder with the star-delta motor connection arrangement described immediately above, wherein the star-delta switch-operating magnet is controlled by a relay, the coil of whichis in series with the excitation circuit of the generator in such a manner that the relay is actuated to energize the star-delta shifting coil so as to shift the switch from star to delta connections when the current in the excitation circuit reaches a predetermined value.

Another object is to provide an arc welder' having a driving motor with a star-delta controlling switch operated automatically by electrical means, this electrical mans being .arranged to be energized in response to the attainment of a predetermined current in the generator excitation circuit, thereby providing a time lag between the instant of starting the motor and the instant at which the star-delta switch is shifted to alter the connections of the motor from star to delta connections.

Another object is to provide an arc welder.

relay being in series with the switch which is operated by the output range switch, the relay coil being arranged to be energized a predetermined period of time after the starting of the motor. 1

Another object is to provide an arc welder of the type described in the paragraph immediately above, wherein the operating coil of the relay is placed in the generator exciter circuit and energized when the excitation current reaches a predetermined value, thereby providing a time lag between the starting time of the motor and the shifting time thereof from star to delta connections.

This is a division of my application Serial No. 111,285, filed November 17, 1936, patented September 20, 1938, No. 2,130,584. 1

In the drawings:

Figure 1 is a wiring diagram for an arc welder embodying the control arrangement of this invention with the star-delta switch connecting the motor stator windings in star connection.

Figure 2 is a wiring diagram, similar to Figure 1, but with the star-delta switch shifted to connect the motor windings in delta connection.

Figure 3 is a side elevation of a portable arc welding outfit embodying the features of the present invention.

Figure 4 is a graphical illustration of the behavior of the arc welder of this invention in its starand delta connections.

Figure 5 is a view of an oscillograph record showing the current draw for a given period of time after starting the motor, using the ordinary across-the-line starting arrangement.

Figure 6 is a view similar to Figure 5, but showing the oscillograph record of the current draw when the motor windings are shifted from star to delta connections, according to the present invention.

GENERAL ARRANGEMENT In general, the arc welding system of this invention consists of a motor-driven arc welder having the motor windings brought out to the terminals of a star-delta switch, means being provided to shift this switch from star to delta connections when the current draw in the output circuit exceeds a predetermined maximum. In the particular embodiment shown herein the energization of the star-delta switch-operating coils is controlled selectively by a relay switch, the operating coil of which is arranged to be energized a predetermined time after the starting of themotor. The particular arrangement shows the relay coil placed in series with the generator exciter output circuit so that the relay is operated to actuate its switch lever and shift the star-delta switch from the star to the delta, position when the exciter has operated a suflicient period of time to produce sufficient current to energize and operate the relay.

Another switch is placed in series with the relay coil and positioned to be operated by the output range switch which controls the output of the generator in such a manner that the series switch is normally open to prevent the energization of the relay, and hence, to disable the stardelta switch from being shifted from its star to its delta position when the current in the excitation circuit exceeds a predetermined maximum. As the output range switch is shifted by the operator to set the generator for a higher output, this series switch is operated by the setting operation when the range switch setting exceeds a predetermined value, thereby closing the disabling or series switch and enabling the relay coil to be energized when the current in the excitation circuit exceeds the amount necessary for causing the relay coil to shift the relay switch.

Hitherto, workers in the welding art have sought to provide an arc welder having a driving motor which is adaptable to wide variations in load requirements so that it may be called upon to pull a 50 per cent to 100 per cent overload, and yet be capable of running idle for considerable periods. It has been recognized that the ideal driving motor for such conditions must be capable of carrying these overloads, yet must have good starting characteristics, a low power factor and low current consumption under a light load or no load at all. In many manufacturing plants, where there are many welders connected to the power line, several of the welders may be running idle due to the workmen changing electrodes or setting up their work. At the same time, however, a heavy drain of current is withdrawn from the power lines and these become overloaded because of this idle operating condition. If the motor is made adaptable to handle the heavy load of maximum requirements, it is found to draw an excessive amount of current when it is being started by an acrossthe-line arrangement.

The present inventor, however, has found that by arranging the motor connections in a stardelta arrangement controlled by a star-delta switch which is operated automatically in response to the attainment of a predetermined current output, he is able to provide a motor which has a low current demand together with a high efficiency and a satisfactory power factor under idling or low-demand conditions, as when a light welding operation is being performed Where the full capacity of the machine is not being utilized. The present inventor has also found that a time lag is preferably provided to allow the machine to build up its speed in star connection before the shift from star to delta connection is made, and brings this about by controlling the shifting or throwover" by a throw-over relay having its operating coil in the generator excitation circuit. A disabling switch is inserted in series with this relay coil to disable the relay from energizing the stardelta switch shifting coils to shift the switch from star to delta positions when the output range switch of the welding outfit is set for an output belowapredeterminedvalue,suchas for example, two-thirds of the maximum output attainable with the outfit. In this manner the setting of the welder for an output exceeding the critical output for the disabling switch enables the motor 6 to start in star connection and to be shifted to delta connection at a period of three'or four seconds afterward, namely, when the excitation current increases to a predetermined amount. If,

however, the output range switch is turned to 10 a reduced setting below the critical amount. the disabling switch is automatically opened, thereby preventing the relay from being energized to cause the star-delta switch to be shifted from its star to its delta arrangement. The machine, 16

under these conditions, starts at a low power consumption and is automatically shifted to the delta connection arrangement when the load demand requires a higher power current consumption.

Arc welder system Referring to the drawings in detail, Figures arranged according to the present invention, Figure 3 showing a portable outfit. In Figure 3 there is shown an arc welder having a housing Ill supporting a rear axle Ii having rear wheels 1, 2 and 3 show a typical arc welding system 25 i2 thereon and secured thereto, as at H. The

housing i0 is also provided with a yoke member i4 pivotally secured thereto, as at I5, and carrying an axle Ii having a single wheel ll secured thereto, as at IS. A handle I! is pivotally secured, as at 20, to the yoke member I and serves 35 the purpose of enabling the operator to pull the outfit from one position to another. The housing It! at one end is provided with a motor sub-housing 2| and at the other end with a generator sub-housing 22. The housing l0 also 0 carries a superstructure 23 having a range switch, generally designated 24, attached thereto. Terminals 25 and 28 are provided for the attachment, respectively, of the welding electrode and ground connections .of the generator.

Also mounted upon the superstructure 23 is a disabling switch 21 arranged to control the energization of a throw-over control relay, generally designated 28, which in turn, controls the shifting of a star-delta switch, generally desigl0 nated 29. The sub-housing 2| contains a motor, generally designated III, whereas the sub-housing 22 contains a generator generally designated ll, both of these being indicated diagrammatically in Figures 1 and 2. Coupled with the motor ll 86 so as to be driven thereby is an exciter 32 for producing the current required for the excitation of the generator field windings 33. connection being made therebetween through the field rheostat reversing switch I4 and the field rheo- 00 stat 35 (Figures 1 and 2). Also included in the exciter output circuit is the winding 26, the operating coil 31 of the relay 2! and the disabling switch 21 operated by the output range switch 24.

The generator output circuit includes the brought out to the range switch contact points 46. The range switch 24 is provided with a switch arm 41 connected by the line 4' to the switch point It and line I, leading to one end of the series windings it. The range switch arm 1 is mounted upon a shaft ll having a cam 52 arranged to shift the lever ll of the disabling switch 21 at a predetermined point on the cam 52, this point corresponding to a predetermined setting of the switch arm 41. From the terminals of the disabling switch 21 the lines I4 and 55 run, respectively, to the exciter output line 50 and to the operating coil 21 of the relay 28, continuing on the opposite side thereof through the line 51 to the exciter output line 58. The latter continues to a connection with one mova'ble switch blade terminal of the field rheostat reversing switch 24, the other terminal being connected to the line It forming a continuation of the line 56 beyond the field rheostat 38. The field rheostat reversing switch 34 is provided with a resistance 60, shunted across two of its fixed terminals, the generator field windings 32 being shunted across the other fixed terminals The motor is provided with a shaft. indicated diagrammatically at I, for operating the gener'ator II and exciter 22. The motor "is of the three-phase type and is provided with stator windings 82, 83 and 64, with the opposite ends brought out to the terminals 85, it, 61, 68, I! and Iii. These terminals 65 to ll, inclusive, form one set of terminals of the star-delta switch 20, the opposite terminals Ii, 12 and I3 being connected to the power current lines II, II and I0. The

star-delta switch 29 is provided with an operating shaft, diagrammatically illustrated at l1 and having mounted thereon the switch blades ll to 83, inclusive. The switch blades 19,." and 83 are interconnected by the conductor 84, whereas the switch blades II, I and 62 are of L-shaped form, insulated from one another. The operating shaft ll of the star-delta switch 29 is connected to means indicated by the numeral II, responsive to the energization of the star magnet N or the delta magnet 81 to shift the shaft I1 and its switch blades 18 to 83, inclusive, from the star position,

shown in Figure 1, to the delta position shown in Figure 2, and vice versa.

Running from one of the power lines, such as the line I5, is a line ll leading to the relay switch blade 89, the fixed terminals and ii of which are connected to the operating coils of the star and delta magnets 86 and 81, respectively, the

opposite terminals thereof being interconnected by the linev 92. A line 02 runs from the power line 14 to the starting switch 04, thence through the stop switch and auxiliary switch 96 to the coils of the star and delta magnets 06 and 81, completing the energization circuit thereof by way of the line I. and relay switch blade 89.

In the arrangement shown in Figure 3 the disabling switch 21 is shown as operated by engagement with a pointer 91 mounted upon the movable dial 98 of the range switch, as distinguished from the cam 52 shown in Figures 1 and 2 for operating the disabling switch 21. In Figure 3 the stardelta switch and the relay 26 are shown in diagrammatic form for clearness of disclosure. In practice, of course, they would be mounted on the superstructure 22 with the parts of the relay 28 concealed by a suitable cover.

Performance characteristics Figure 4 shows graphically the performance of a typical welding system constructed and arranged is shown in Figures 1 and 2. The horizontal values (abscissa) represent generator output in amperes at 40 volts, whereas the vertical values (ordinate) represent, according to the particular sets of curves, the motor ampere draw, the percentage emciency, or the percentage power factor. From this graph it will be seen that the motor in star connection has a very low current draw in the lower ampere outputs, as compared with the delta connection, whereas in the higher ampere range the delta connection has the lower current draw. The present invention takes advantage of both of these factors by employing the star connection for the lower current outputs with a low motor current draw, and the delta connection for the higher ampere outputs. These two curves are designated Star amps" and "Delta amps, respectively, in Figure 4.

The middle set of curves, designated Delta eff" and Star eil'-,- represent the comparative emfactor under varying ampere outputs of the generator at 40 volts. It will be seen from these curves that the delta connection has a much lower power factor than the star connection at low ampere power factor in this neighborhood. In the higher generator outputs, however, the delta connection gives a higher power factor than the star connection. The present invention also takes advantage of these circumstances to provide the most efliclent arc welding system at both low and high ampere outputs.

Figure 5 shows the oscillograph record produced by the oscillations of the oscillograph during the starting and subsequent period of operation for the ordinary across-the-line arrangement. This record shows that the motor initially darws 1'16 amperes for a period of 1.62 seconds before this large current draw tapers oil to the l6-ampere draw subsequently obtained. This record was produced by an oscillograph employed with a 200-ampere arc welder with an across-theline type of starter.

Figure 6, in contrast, shows the same are welder employed in connection with the star-delta arrangement of the present invention. The record of Figure 6 shows the starting current when the machine is started and before subsequent behavior, in a manner similar to Figure 5. In Figure 6, however, the motor is initially connected in the star arrangement and its current draw for the initial period of 5.1 seconds is merely 58 amperes, in contrast with the 176-ampere current draw in Figure 5. As this current draw tapers off the throw-over devices operate to throw the system into a delta-connection, whereupon the current ing job is a light one, the welder is operated exclusively in a star connection so that it consumes but 58 per cent. of the current which wouldbe consumed in a delta connection.

outputs, the star connection giving a much higher Operation The operation of the arc welder of this invention is largely apparent from the foregoing description. In operation the motor 30 is started with the circuit in the star arrangement, as shown in Figure 1, it being assumed that a light welding job is to be done. Under these conditions the range switch 24 is set with its switch arm 41 at a point below the point where the disabling switch 21 becomes closed so that the circuit through the operating coil 31 of the throwover control relay 28 is open. As the generator 3| and exciter 32 come up to speed and produce current the throw-over control relay 28 is inoperative to effect the energization of the delta magnet Bl, hence, the star magnet 88 remains energized and the delta magnet 81 deenergized. The switch blades of the star-delta switch 28 then remain closed, in the star position shown in Figure 1. and the subsequent operation occurs with the star connection of the motor stator windings. With the arrangement, therefore, as shown .c the motor will ccns much. lower a'ncunt oi current than would \1-19 case ion because the w toad v small proportion of of the welding outfit. ever, th he range 3 cars [-2 and close the disabling occurs the coii er control relay EC osses into a the excite: 3?, rec

erg oper amount of c= he ere: to. as before, "out do tiai s operation the dec the position shown [is e generator and the .er, after a period of three or up V Y fou erzciter produces enough curren the elay coil "5 and cause the rela to be shifted from the terr This action cleanergize .ogne't 36 and energizes the delta result of this the motor stator shown in Figure l, and recon-= nect ta arrangement, as shown in.

:1 occurs automatically without t e -c t of any attention on the part of toe operator ot than to set the range switch 3 at the desired output.

It will be understood that I desire to compr t i1.. my invention such modifications as -1. to scope of the claims and the in Patent, is:

1. in combination, a driving motor, a generator driven thereby, means for connecting the mo tor windings selectively in star anddelta arrangements, and responsive to the attainment of a precieter .ied generator current output for shiftin connecting means from star arrangement to delta arrangement.

2. "in combination, a driving motor, a generator driven thereby, means for connecting the motor windings selectively in star and delta arrangements, and means connected to the generator output circuit and responsive to the expiration of a predetermined period of time after the starting the motor in one arrangement for shifting said connecting means to the other arrangement.

3. In combination, a driving motor, a generator driven thereby, said motor having a stator with a plurality of windings, means for connecting said windings selectively in star and in delta arrangements, and electrically-operated means responsive to the attainment of a predetermined generator output for shifting said connecting means from one arrangement to the other arrangement.

4. In combination, a driving motor, a. generator driven thereby, said motor having a stator with a plurality of windings, switch means including an electromagnetic switch operator for connecting said windings selectively in star and in delta arrangements, and means responsive to the attainment oi a predetermined generator current output to selectively energize said operator for shifting said connecting means from one arrangement to the other arrangement.

5. In combination, a driving motor, a generator driven thereoy, said motor having a stator with a plurality ot windings, :switc means includingan electromagnetic switch operator for connecting windings selectively in and delta arrang and relay normally o erativc to o W t range-merit p-redeterr ing of the 1 energies necting means to L 6. In .ation a d ving motor, a generator driven ti? r. it-h "innings of motor being adapted to ch ed from. a starting arrangemer I a r.-duced voltage per turn is 'igernent in which nor- .ied, means responsive edetermlned generator current or. 7 mg a change irom one arrangement of rngs to the other arrangement, a smtchng mechanism for completing said change, said mechanism comprising two sets of rotating contact members, the contact members of set connected together and the con act memoem of the other set being insulatest from one a r. and magneti means responsive to said can. means for rotating said members from in which the motor windings are c a position in W a delta error gs pressed. across nan of the motor windings is changed from a value to normal value after a starting period dependent upon the attainment of a cdetor: ed generator output.

7. In ccin'cir" n, a power generator, an exciting generator for ing the field oi the power generator, a motor driving said generators, motor having w ndings adapted to be selectively co sue? at a reduced voltage per turn is appmd drlrlr e starting period of the motor and a normal voltage per turn after the starting and means responsive to the voltage developed by the exciting generator for changing the Inc-tor winding connections from the reduced voltage per turn condition to the normal. voltage per turn condition.

8. In combination, a power generator, on exciting generator for energizing the field of the power generator, a motor for driving said generators, means for connecting the motor windings respectively in star and delta arrangement, and means responsive to the output current of said exciting generator for shifting said appiied to a. rm?" mal volta e to the at 10. In combination, a power generator, an exciting generator for energizing the field of the power generator, a motor for driving said generators, means for connecting the motor windings selectively in star and delta arrangement, 5

and means including a relay connected in the field circuit of the power generator and in the armature circuit of the exciting generator for shifting said connecting means from the star arrangement to the delta arrangement.

EDWARD A. HOBART. 

